Newshub graphic reveals Auckland's deadly volcanic field

Scientists have been trying to project what would happen to Auckland if a volcano erupted. Credits: Image: Getty; Video: Newshub

Auckland's volcanoes have been revealed in stunning new graphic showing the size of the deadly volcanic field.

Scientists say the young field is forecast to erupt again and preparations are already beginning for the next eruption. But experts warn if something does go wrong, there won't be much time to evacuate.

Auckland is the only large city in the world built directly on top of a volcanic field and it comes at a cost.

There have been more than 55 eruptions in Auckland over the past 190,000 years, but experts say it's impossible to know when or where the next big one will hit. However they warn the results would be catastrophic.

The Newshub graphic below shows how close you are to one of the towering volcanoes. Rangitoto is the only one that's erupted more than once, and last blew about 550 years ago. Click on the arrows to guide you through the graphic.

"What we do know is it is certainly a case of 'when' rather than 'if', and that the location of the eruption will be within the current bounds of the volcanic field, which will almost certainly impact Auckland," she says.

Scientists say it'll probably start with a series of jolts.

"The seismographs around Auckland is our key tool in determining when we start seeing earthquakes like that and if we're starting to see any rise in that magma," researcher Thomas Wilson says.

"Maybe once we had detection that there's been magma on the move, we might have as little as a few hours."

University of Auckland volcanologist Professor Shane Cronin says current technology wouldn't detect the magma until it was about 27km from the surface - leaving little time for residents to get out.

"This work doesn't change the likelihood of eruptions - but it does change our certainty around how much warning we could potentially have," he told NZME.

Previous research by University of Canterbury researchers examined what would happen if there was a two-month-long volcanic eruption near Mangere Bridge, south of Auckland's CBD.

Their paper concluded the volcanic eruption would destroy anything up to two-and-a-half kilometres away, and would leave transport networks crippled and a third of the population reduced to refugees. It could also generate a 2m-high tsunami around the harbour.

Evacuating an area of central Auckland with a 5km radius - about 78 square kilometres - would require moving up to 435,000 people.

The Earthquake Commission is funding research into the effects of an eruption in Auckland, and how the risks can be managed.

But when Newshub hit the streets in 2017, everyone admitted they weren't prepared for an eruption.